Safety systems for early lighting of stop lights in vehicles (hereinafter shortly referred as the "systems") are well known in the vehicle industry, and have become an integral part of many vehicles The systems try to foresee when the driver releases the pressure on the accelerator pedal or shortly thereafter, if he intends to activate the brakes, and if so, immediately to light the rear stop lights. If the system determines that the driver released the acceleration pedal with no intention to activate the brakes, no early lighting is activated. These systems can normally reduce approximately 0.250 second from the interval between the time that the driver decides to brake until the stop lights are actually lighted, a reduction that in many cases can be critical Examples for such systems can be found in U.S. Pat. No. 3,089,129, U.S. Pat. No. 3,501,742 and U.S. Pat. No. 4,916,431. Such systems are based on the discovery that a driver releases the acceleration pedal in a different manner when he only intends to decelerate with no intention to activate the brakes, or when activation of the brakes follows. Most systems anticipate the driver intention by sensors which are mounted on the gas pedal or on fuel supply systems and measure the rate of negative change in the fuel supply (hereinafter the terms "sensor" or "sensors" intend to indicate means for measuring the negative rate of change in the fuel supply to the engine). For example, U.S. Pat. No. 4,712,098 describes a system comprising an inertia sensor mounted on the accelerator pedal. In other systems a sensor is mounted on the lever which connects the accelerator cable to the carburetor. In most of the systems, an electronic signal which is relative to the rate of negative change in the fuel supply is provided, and if the signal level is above a predetermined threshold, the system immediately activates the stop lamps. Of course, the predetermined threshold level is a critical parameter which should be carefully selected.
However, systems of this type have been found to suffer from many false alarms. The term "false alarm" when used herein is intended to indicate cases in which the brake lights are switched on by the system when the driver has no intention to activate the brakes. Such failures of estimating the driver's intention can even be dangerous, when false lighting of the stop lights cause drivers of following vehicles suddenly to activate their brakes, when this is not necessary, and in some cases accidents may occur. One way for reducing the number of false alarms is to increase the threshold level, but this can cause the system not to operate when its operation is required.
It is a purpose of the invention to increase the reliability of systems for early lighting of stop lights by reducing the number of false alarms. Specifically, the invention intends to reduce or eliminate the number of times in which the system early lights the stop lights, when brake activation by the driver does not follow.
It is an object of the invention to adapt the system to specific drivers who may drive the vehicle, more partly, to provide a system that will learn the driving behavior of specific drivers, and accordingly establish a specific threshold for each driver.
It is also an object of the invention to provide said improvements at a relatively very low cost and low volume.
Other purposes and advantages of the invention will become apparent as the description proceeds.